Liquid-cooled load for a coaxial transmission line



June 26, 1956 J. R. BIRD ET AL LIQUID-COOLED LOAD FOR A COAXIAL TRANSMISSION LINE 4 Sheets-Sheet 1 Filed Jan. 26, 1949 June 26, 1956 Filed Jan. 26, 1949 I 4/ I 39 37 1 55 38 55 1 34 47 "42 52 H I 56 45 J. R. BIRD ET AL LIQUID-COOLED LOAD FOR A COAXIAL TRANSMISSION LINE 4 Sheets-Sheet 2 ATTORNEY June 26, 1956 J. R. BIRD ET AL 2,752,572

LIQUID-COOLED LOAD FOR A COAXIAL TRANSMISSION LINE Filed Jan. 26, 1949 4 Sheets-Sheet 3 INVENTORS JAMES R. BIRD 7 HAROLD E. STEVENS Fig. B BL SSY D. FREDERICO United States Patent LIQUID-COOLED LOAD FOR A COAXIAL TRANSMISSION LINE James R. Bird, Chagrin Falls, and Harold E. Stevens and Blossy D. Frederico, Cleveland, Ohio, assignors to Bird Electronic Corporation, Cleveland, Ohio, a corporation of Ohio Application January 26, 1949,, Serial No. 72,782 34 Claims. (Cl. 333-22) This invention relates to electrical devices for use in high frequency electrical apparatus. There are many applications in the field of high frequency electrical circuits for devices capable of absorbing electrical power. Particularly desirable are power absorbing devices which exhibit substantially constant impedance characteristics over wide frequency ranges and Which react as lines of infinite length without reflections or standing waves. Resistive devices having certain of the characteristics mentioned for terminating high frequency coaxial lines and for serving as so called dummy loads have previously been proposed, reference being made to copending application for patent Serial No. 692,116 filed August 21, 1946, now U. S. Patent No. 2,552,707. Such devices customarily employ a cylindrical inner resistive element in combination with a tapered or horn shaped outer conductor, or equivalent, combined in a coaxial line unit. Coaxial resistive units of this type have been immersed in a liquid dielectric-coolant as shown in copending ap plication Serial No. 777,516 filed October 2, 1947, now

U. S. Patent No. 2,556,642, obtaining advantages such as increased power absorbing capacity.

It has been found in practice, however, that the electrical power which can be safely and practically absorbed by units of the type referred to is limited, necessitating units of large or excessive size and resulting in increased costs to satisfy present commercial needs.

It is therefore one of the principal objects of the present invention to provide a generally improved resistive or line terminating device of the character mentioned which exhibits increased power absorbing ability in combination with substantially constant characteristic impedance over a wide frequency range. Among the improvements incorporated in the present liquid dielectriccoolant coaxial line device are: means for limiting the loss of dielectric-coolant liquid so that liquids of relatively low boiling point may be employed, means for baflling the liquid container or casing to provide separate chambers connected for serial flow of liquid through the dielectric space between the conductors of the coaxial line unit, and means for incorporating a thermo responsive safety switch in the unit for the purpose of de-activating the equipment with which the device is employed in the event of an excessive temperature increase. More specifically the invention provides a high frequency power absorbing device of the tapered conductor type employing a liquid dielectriccoolant in which provision is made for improved dielectric-coolant flow to obtain more uniform and more efiicient cooling of the conductors of the unit, the power absorbing characteristics of the device being thereby relatively increased. As a preferential arrangement the conductors of the coaxial line terminating unit that absorbs the power are disposed with their axis vertical and are immersed in aliquid dielectric coolant, provision desirably being made for dielectriccoolant flow as by convection through the space between the conductors, the convective flow of liquid being improved by employing a chimney effect to induce an increased flow of liquid over the parts of the coaxial line unit that are to be cooled.

Another object pertaining to the power absorbing aspects of the invention is concerned with improvements in the coaxial line terminating unit which provide for increased flow of liquid dielectric-coolant through the space or spaces between the conductors at the small diameter end of the coaxial line unit. More specifically the tapered or horn shaped conductor which normally curves into and tangentially contacts the resistive coating on the cylindrical inner conductor in accordance with accepted theoretical design principles is, in the present arrangement, formed with a cylindrical portion at its small diameter end, providing an annular, substantially uniform clearance space between the conductors for the flow of cooling liquid dielectric, the variation in capacitance from the theoretical being compensated by an auxiliary or supplemental conductor electrically connected to the small diameter end of the tapered horn and arranged to cooperate with the resistive coating on the cylindrical inner conductor as by being disposed internally of the inner conductor to provide capacitance substantially equivalent to that lost by departure from theoretical design principles.

Another object is to provide a coaxial line device of the character mentioned in which the conductors supported with their axes vertical, are immersed in a relatively deep body of liquid dielectric coolant, the rate of coolant flow over the conductors of the line unit being relatively increased as by a chimney bafiie within the coolant in line with the axis of the unit, the chimney or stack being arranged to receive heated liquid from the conductors of the unit to confine and guide such heated liquid for upward movement in the body of liquid dielectric-coolant. Heated liquid flowing out the top of the chimney returns to the coaxial line unit through a passage or chamber on the outside of the chimney, the returning liquid being cooled as by auxiliary refrigerated coils preferably located adjacent the top of the chimney.

A still further object of the invention pertains to the cooling of the heated conductor of a coaxial line resistor and aims to provide a device of the character mentioned in which a liquid dielectric-coolant is employed having a boiling point suificiently low to result in the continuous formation of gaseous particles or bubbles at the surface of the heated conductor, the latent heat or vaporization of the liquid thus being utilized in the cooling process. The gas particles or bubbles liberated from the hot conductor and rising through the liquid serve to augment or aid the upward fiow of the liquid dielectric-coolant through the chimney thereby improving the general flow rate throughout the system and increasing the rate of flow over the conductor being cooled.

Measurement of high frequency power such as that absorbed by a line terminating unit or dummy load of the character mentioned is a further objective of the invention. It is sought to provide an electrical measuring instrument or wattmeter which accurately indicates the power absorption or energy absorbing rate of the device over a relatively wide frequency range and by means of which instantaneous readings can be readily made as 'desired. As a preferential arrangement a line terminating unit of the constant or uniform characteristic impedance type is combined with a capacitance voltage divider of improved design and construction and with an electrical current measuring instrument such as a galvanometer. The galvanometer is energized by sample current through the voltage divider, the current being suitably rectified and maintained substantially at peak potential as by establishment of a proper galvanometer circuit time constant obtained through resistance in such circuit.

Other objects and advantages pertaining to certain details of construction and arrangements of parts to obtain simplicity and economy in design and construction are set forth in the following detailed description of a suitable embodiment of the invention. This description is made in connection with the accompanying drawings forming a part of the specification. Like parts throughout the several views are indicated by the same letters and numerals of reference.

In the drawings:

Figure 1 is an elevational View, partly diagrammatic, of a high frequency coaxial line terminating device or dummy load in combination with a voltage divider, the combination being employed in the electrical measuring device or wattmeter of the present invention;

Fig. 2 is a top plan view of the device, partly in section, taken substantially along the line indicated at 2-2 of Fig.v 1 and enlarged with respect to that figure;

,Fig. 3 is a sectional detail, with parts removed, taken substantially along the line indicated at 33 of Fig. l and enlarged with respect to that figure;

Fig. 4 is a fragmentary elevational detail of the upper or small diameter end of the coaxial line unit showing the slits for convective flow of the cooling liquid dielectric;

Fig. 5 is a fragmentary vertical sectional view, partly diagrammatic and with parts removed, taken substantially along the line indicated at 5--5 of Fig. 1 and enlarged with respect to that figure;

Fig. 6 is a fragmentary vertical sectional view with parts removed taken substantially along the line indicated at 6-6 of Fig. 1 and enlarged with respect to that figure;

Fig. 7 is an enlarged vertical sectional detail through the voltage divider or current pick-up showing the manner in which it is mounted on the transition or connector section of the coaxial line terminating unit;

Fig. 8 is a diagrammatic representation of the electrical high frequency energy measuring device or wattmeter of the present invention showing the electrical connections between the components;

Fig. 9 is an enlarged sectional detail, with parts removed, taken substantially along the line indicated at 9-9 of Fig. 7;

.Fig. 10 is an enlarged elevational detail, partly dia grammatic, partly in section and with parts broken away and removed, showing the voltage divider or sampling component and means for connecting the same to the voltage responsive device or galvanometer; and

Fig. 11 is an enlarged fragmentary detail showing the resistor and the bottom capacitor in section.

General The present combined high frequency line terminator and electrical energy measuring device or wattmeter incorporates a resistive coaxial line unit A supported with its axis vertical or substantially so in the lower end of a casing assembly or liquid container B. On the tapered transition or connector end of the coaxial unit A is mounted a voltage sampling device D which incorporates a capacitance voltage divider and a rectifier. Power or energy, being related to impressed voltage, is measured and visually or otherwise indicated as by an instrument such as a galvanometer, preferably of the dArsonval type, connected to .the voltage sampling device D as will later appear and responsive to the rectified voltage.

The casing assembly B comprises a vertically elongated outer casing or housing 1 which may be in the form of a cylindrical metal tube of uniform circular cross section throughout its length. Brackets 2 are secured to the outside of the tube as by welding or brazing and are apertured to receive screws or other fasteners for mounting the device vertically on a wall or instrument panel. The lower end of the casing tube is closed by a circular metal disc 3 formed with a circular center opening to receive the coaxial line unit A. In securing the closure disc 3 in the lower end of the casing 21, as in making similar connections between other permanently joined metal parts of the apparatus, soldering, brazing or Welding is em? ployed, using conventional techniques.

Coaxial resistor The coaxial line unit A is constructed generally in accordance with theoretical considerations and principles heretofor set forth in the copending patent application referred to and another patent application Serial No. 692,116 filed August 21, 1946, with certain modifications and improvements. An outer tapered conductor or horn 5 of brass or similar metal is formed at its large diameter end with an integral cylindrical extension 6 that is slidingly received within the circular opening in the casing disc 3. A tapered or frusto-conical connector 7, formed as by spinning or stamping brass or similar thin metal, is disposed as a continuation of the conductor 5 with its large diameter end connected to the large diameter end of the horn conductor. The' connector is formed at its large diameter end with an offset cylindrical flange 8 which embraces the end of the cylindrical portion 6 on the outer conductor 5. The circular end of the conductor portion 6 abuts a shoulder formed by the radial offsetting of the connector flange 8 to provide a transition between the inner surfaces of the parts without an objectionable diameter change, thereby avoiding undesirable reflections which would impair the electrical characteristics of the device. The cylindrical conductor portion 6 is secured in the circular socket thus provided as by solder which flows across the joint and further improves the electrical transition.

An obliquely disposed circular edge flange 9 on the cylindrical portion 8 of the outer connector and a matching frusto-conical oblique surface on an integral flange 11 which surrounds the circular opening in the casing closure disc 3 are embraced by a split clamping ring 10, V-shaped in cross section. Lugs or cars 14 secured in confronting relation on the ends of the split clamping ring are drawn together by a screw 12 to tighten the ring about the flanges 9 and 11, drawing the latter against an interposed rubber 0 ring. The coaxial line unit A is thus held in predetermined fixed relation and sealed in the bottom of the casing unit B.

At its small diameter end the connector 7 is formed with a tubular cylindrical portion 15 which receives a turned fitting 16 of brass or similar metal. To this fitting is secured an externally threaded sleeve 17 which holds, as by a press fit, an insulating plug 18 of suitable shape retaining, relatively stilf, pliable, plastic, dielectric material such as polytetrafluoroethylene having a dielectric constant substantially the same as the liquid used in the casing. The metal sleeve 17 has a collar 15 welded or brazed on one end, the collar having a circular rabbet which receives a pilot fiange on the fitting 16 to hold the parts in correct axial alignment. Screws 26 extend through spaced axial apertures on the collar 19 and are threaded into the fitting 16. The joint is made fluid-tight as by an O ring 21 of rubber or the like that is compressed between the end of the sleeve 17 and a flanged retainer ring 22 seated against a circular shoulder in the fitting 16. The circular flange on the retainer 22 engages one end of the dielectric plug 13 to locate the latter and to resist axial movement of the plug into the interior of the connector '7.

Extending longitudinally through and coaxial to the tapered conductor 5 and the connector '7 aligned therewith is an inner conductor assembly. This assembly includes a dielectric core or tube 24 of electrical porcelain or other suitable ceramic material. This core is of substantially uniform circular cross section throughout its length and is externaly coated by chemical reduction, cracking, or otherwise with a uniform conductive film of carbon or carbonaceous material. Although the carbon film is referred to as a conductor it is a conductor of relatively high resistance, the resistance preferably being substantially uniform per unit of length from end to end of .5 thtube 24. It is the resistance olfered by this coating or inner conductor of the coaxial'line unit to the how of electricity or current that converts to heat the electrical energy to be absorbed bythe device.

At each end the tube 24 is coated with an annular band of conductive metal paint which extends onto .the carbonaceous coating and serves .as a means for making electrical connection to the resistive film. The conductive paint band on the lower end of the ceramic tube is positioned within the cylindrical end portion 6 of the tapered horn 5. This end of the ceramic tube is turned or ground to provide a reduced diameter portion telescopically received within a hollow or tubular cylindrical portion on the large diameter end of atapered metal connector 27. The tapered connector 27 extends axially through the tapered outer connector 7 and is formed or fitted at its small diameter end with a cylindrical rod 28 that is embraced and supported by a dielectric plug 18. The endof the rod 28 is split axially and bored out or otherwise formed for connection to the center conductor of aconventional coaxial electrical line. The threads on the tubular sleeve 17 receive the internally threaded collar of the coaxial line so that the outer conductor of such line makes electrical contact with the sleeve 17. Thus power to be absorbed or measured by the present device can be fed into the lower end of the coaxial line unit through a conventional coaxial cable attached to the tubular sleeve 17 and the rod 28.

Electrical connection between the cylindrical portion 26 of the inner connector and the conductive band 25 on the lower end of the inner conductor tube 24 is attained as by soldering or preferably by an expansible band 29 which embraces both the connector portion and the conductive paint. This band is formed of resilient spring metal such as beryllium copper and is preferably arched across its width. Axial slots open alternately through opposite edges of the band at spaced intervals about the band circumference and permit yielding radial expansion. By reason of being formed to a slightlysmaller diameter than that of the tube and connector, the band tightly grips the parts.

Theoretical considerations set forth in the copending applications referred to prescribe that at the upper or small diameter end of the resistive coaxial line terminating device the logarithmic curvature of the tapered outer conductor be such that the inner surface of such conductor approach the cylindrical conductive coating on the center tube 24 in a substantially tangential curve. In constructions wherein the tapered outer conductor approaches the inner conductor in a tangential or similar curve, liquid cooling of the resistive coating forming the inner conductor is extremely difficult at and adjacent the region .of tangency. It is believed that in such constructions liquid dielectric-coolant may fail to completely fill the narrow space or spaces between such tangentially contacting conductors, or if a liquid having a relatively low boiling point is used, bubbles or gas vapor particles subsequently formed by the heat developed in the resistor displace the liquid coolant and become lodged or trapped in the narrow spaces between the conductors. Such gas vapor bubbles or particles act as insulation impairing the heat transfer to the liquid.

In the present invention the liquid dielectric-coolant contained in the casing 1 is admitted to space 31 between the inner and outer conductors of the coaxial line through elongated axial openings or slots 30 formed in the tapered outer conductor '5. These openings are arranged in groups along the length of the conductor and the openings of each group are uniformly spaced circumferentiallyabout the conductor. At the upper or small diameter end of the coaxial resistor unit the outer conductor 5 is formed with a cylindrical end portion 32, the inner surface of which is separated from the outer conductive coating on the tube 24 by an annular space 36 preferably uniform in radial depth along the length of the cylindrical portion portion 35 of the latter.

32. For capacitance compensating purposes a tubular metal sleeve or element'33 of substantially the same length "as the cylindrical portion of the-outer conductor is mounted coaxially within the upper end of thecenter conductor 24. The metal element 33 has axial slots, oneof which is indicated at 34, and is initially formed to a diameter slightly greater than the inside of the ceramic tube 24 so that in assembly the tubular element is slightly compressed and held firmly against the inner walls of the ceramic tube by the inherent resiliency of the metal.

At its upper endthe cylindrical portion 32 of the outer conductor 5 is joined to an integral reduced diameter cylindrical collar 35 which is axially split and by inherent resiliency or a suitable circular metal clamp (not shown) tightly embraces the painted on conductive coating 25 applied to the carbonaceous or resistive coating on the ceramic tube 24. A matching reduced diameter portion 37 is formed on the upper end of the tubular element 33 internally of the holding collar portion 35, providing clearance 38 between the ceramic tube and the metal of the internal tubular element which permits the metal parts to deform slightly in assembly thereby avoiding cracking and crushing of the ceramic tube. An inturned circular flange 39 on the tube gripping portion 35 of the outer conductor embraces the reduced diameter end of the tubular element 33 against a collar 41 formed on the latter, the parts being secured together as by brazing or soldering.

In constructing the device the tubular element is secured in the end of the outer conductor 5 after which the cuts 34 in the tubular element and similar cuts or slots 40 in the outer conductor are formed as by a saw. The ceramic tube is inserted axially through the outer conductor 5 and is received telescopically over the tubular element 33. The end of the ceramic carrying the conductive metal paint coating is received and gripped in the reduced diameter gripping portion 35 the latter being slightly expanded in the assembling process. The length of the outer conductor 5 and the zone of contact between the outer conductor and the conductive coating on the tube '24 corresponds to the theoretical considerations governing the design of coaxial line devices employing a logarithmically curved outer conductor. In lieu of the tangential contact between the inner surface of the conductor '5 and the conductive coating on the inner tube 24 as provided pursuant to theoretical design by continuance of the logarithmic contour of the horn 5 to the contact zone between the parts and as indicated by broken .lines 42 of Fig. 5, the present invention utilizes the cylindrical portion 32, the inner surface of which is spaced outwardly from the theoretical contour, thus providing the uniform annular clearance space 36. This .space is of sufficient thickness to permit the circulation therethrough of liquid dielectric coolant so that ample cooling is provided at the small diameter end of the device for withdrawal of heat from the conductive coating on the-center core 24. The tubular insert 33, electrically connected to the outer conductor 5 at the upper end of the latter augments or supplements the capacitance between the outer conductor and the coating on the ceramic tube 24 to compensate for the reduction in capacitance resulting from spacing the outer conductor, throughout the region of the cylindrical portion 32, outwardly from its theoretical position. The broken lines 42 indicate the theoretical contour of the outer conductor of a corresponding device constructed in accordance with the fundamental design principles governing this type of coaxial ohmic line terminating device. Thus, in lieu of tangential contact between the inner and outer conductors of the coaxial line the outer conductor of the device of the present invention is curved or formed sharply or abrutly into the conductive surface on the cylindrical tube '24 in the region of annular shoulder 43 which joins the cylindrical portion 32 of the outer con- .ductor to the reduced diameter gripping or contacting Chimney baflle Within the casing 1 and dividing the interior thereof into an inner chamber 45 and an outer or surrounding annular chamber 46 is a tubular chimney baffle 47 which is supported on the outer conductor 5 of the resistive coaxial line unit. The lower end of the bafiie makes circumferential line contact with land portions of the conductor horn at an intermediate point of the latter. The casing chambers 45 and 46 are thus sealed from one another at the lower end of the baffie 47, flow of liquid from the bottom of one chamber to the bottom of the other necessitating flow through the space 31 between the inner and outer conductors of the resistive coaxial line. To permit flow from one casing chamber to the other a number of the elongated slots 30 are disposed or extend below as well as above the region of contact between the bafile and the conductor horn. Centering the baflle 47 in the casing 1 and holding the baffle against longitudinal shifting movement in shipment are a number of U-shaped metal spring elements 48. These spring elements are riveted to the bafile and bear resiliently against the inside cylindrical surface of the tubular casing.

Cooling coil In the upper end of the casing a double helically arranged tubular cooling coil 50 surrounds and locates the baffle 47. This coil preferably is arranged in inner and outer concentric banks or runs and is disposed substantially wholly in the outer chamber 46. The ends of the cooling coil extend upwardly and are received in spaced parallel rigid metal tubes 51 and 52 secured vertically in a top closure disc 53 sealed across the upper end of the casing as by a V-sectional clamping ring 54 arranged similarly to the bottom clamping ring previously mentioned. The ends of the coil tube 50 are sealed within the tubes 51 and 52 at or near the top ends of the latter and, when the device is in use, coolant from a suitable source of supply is forced into the coil through the tube 52, exhausting through the tube 51. A vent 55 is secured in the inlet tube 52, communicating with an annular space between the inside walls of such tube and the coil tube 50 below the seal between the tubes. The vent 55 is in the form of an internally threaded tubular fitting secured over an opening in the tube 52 and having an opening or hole through which gas or vapor is vented from or admitted to the space above the top surface level, indicated at 56, of liquid dielectric coolant in the casing. This breathing or venting action takes place under the influence of pressure differences resulting from expansion and contraction of the liquid when subjected to temperature changes in use. A closure plug, not shown, is screwed temporarily into the vent fitting 55 during transit to prevent lossof liquid. As a preferred arrangement,

the cooling coil 50 is provided with a fin or fins for increased heat transfer efficiency. One of the fins, which extends into the annular space between the cooling coil and the cylindrical inside wall of the inlet pipe 52, is in the form of a continuous spiral or helix which has a relatively close fit within the tube 52. By this arrangement a continuous spiral passage is formed between the tubes by the fin, the passage extending from the gas space within the casing chamber to the opening in the vent 55. Volatilized dielectric-coolant which is forced upwardly through such spiral passage in the inlet tube 52 is subjected over an extended spiral path to the cooling action of fresh coolant flowing into the cooling coil. The resulting chilling condenses the Volatilized dielectriccoolant and the condensed liquid flows down the spiral passage formed by the fin and tubes to return to the chamber. Loss of Volatilized dielectric-coolant is thus minimized; the necessity for frequent replenishment is avoided. For filling the container with liquid dielectric-coolant, an opening is provided in the top closure plate 53, this filler opening normally being sealed by-a plug 58 and an 0- 8v ring which embraces the plug bore in the opening.

Thermal safety switch Extending downwardly through the center of the casing chamber in axial alignment with the resistive coaxial line A and into the upper end of the tubular baflle 47 is a thermo responsive safety switch indicated at 60. This switch is of the type comprising a tube 61 containing electrical contacts which function to open or separate when the tube is subjected to temperatures above that for which the device is set. The thermo safety switch is fitted at its upper end with a threaded plug 62 secured in a threaded central aperture in the top closure disc 53. The switch contacts are internally connected to insulated binding posts 63 on the top of the plug 62. These posts serve as terminals for electrical wires 64 which are included in the series safety circuit of any electrical apparatus with which the present device is employed. Upon an increase in temperature above a predetermined safe limit of the liquid dielectric-coolant in the casing 1, as might result from failure of coolant circulation through the coil and as determined by the setting of the thermo switch 60, the contacts in the latter are automatically opened to interrupt the series safety circuit and shut down the apparatus in accordance with conventional practice.

and seats in the counter- Liquid dielectric-coolant The coaxial device of the present invention whether in the form of a dummy load or a wattmeter may be utilized effectively with various liquids employed as the dielectriccoolant in the casing 1 and in the space 31 between the inner conductor 24 and the outer conductor or horn 5. Suitable liquids include the various mineral oils and oils such as those used in electrical transformers. The dielectric constant of the particular dielectric-coolant employed is taken into consideration in calculating the dimensions of the coaxial line B by applying well known theoretical principles such as those outlined in the copending applications referred to, particularly in determining the taper or shape of the outer metal conductor 5. Liquid dielectric-Coolants of the mineral oil type cool the center conductor by contacting the latter and carrying away absorbed heat in convection currents. When operating coaxial line devices of the type herein contemplated under high electrical loads, the temperature gradient between the inner resistive conductor 24 and the cooling liquid dielectric may become objectionably high and may even result in failure of the ceramic tube on which the center conductor 24 is coated.

It has been found that by using a heavy or high density liquid dielectric-coolant having a relatively low boiling point it is possible to utilize the heat of vaporization of the liquid to absorb large quantities of heat without objectionable temperature rise in the center conductor 24. It has also been found desirable to employ a low viscosity liquid so that rapid convective flow is obtained.

Although various liquids such as high temperature liquid silicones are suitable for use as dielectric coolants, it has been found to be particularly advantageous to employ liquid halogenated hydrocarbon, preferably saturated and non-inflammable, having a relatively low boiling point such as from about C. to about 160 C., preferably in the range of from about C. to about C. It is also desirable because of practical considerations in the physical shape of the born 5 to employ a liquid having an absolute number specific inductivity or dielectric constant preferably less than 3. Suitable liquids of the family mentioned, are fluorinated and chlorinated aliphatic hydrocarbons, particularly the latter. A satisfactory compound or liquid having properties falling within the desired ranges is tetrachlorethylene having a specific inductivity or dielectric constant of about 2.3 and a boiling point of about 119 C. Other liquids which may be used are carbon tetrachloride, tetrachloroethane, pentachloroethane, trichlorethylene and 1, -1, 2-trichloroethane. Compounds such as fluorotr'ichloro'ethylene and trichlorobromo methane can be used though less desirable than those previously mentioned.

In being converted from liquid to vapor the coolantdielectric extracts from the heated resistive center conductor an amount of heat represented by the vaporization heat of the liquid volume converted into vapor. Thus high density or specific gravity and high specific heat are also desirable properties present in the particular coolant dielectrics mentioned. Vaporizing of the liquid in this manner results in the continuous formation over the surface of the center conductor 24 of vapor bubbles which break away from and are conducted away from the heated surface and rise through and with the liquid allowing additional or fresh coolant liquid to approach and contact the conductor surface to cool the latter. In a device constructed as described, this action is extremely rapid, particularly when a low viscosity liquid such as tetrachlorethylene is employed, and has a pronounced cooling etfect on the center conductor. The cooling effect is particularly eflicient by reason of the vertical positioning of the axis of the resistive coaxial line. The elongated inner chamber 45 defined by the baffle 47 provides a tall chimney effect through which the heated liquid dielectric coolant rises and through which also rises the gas or vapor bubbles or particles of volatilized liquid. The gaseous bubbles or vapor particles being buoyant accelerate the upward movement and promote a faster circulation of the liquid body upwardly through the center chamber 45 and by reason of convective forces, downwardly through the outer or annular chamber 46 than is obtained by a coolant that remains liquid throughout the circulation cycle. Hence the entire circulation of the liquid through the casing chambers is increased or accelerated over that prevailing in a similar arrangement employing a liquid dielectric-coolant having a relatively high boiling point or a relatively high viscosity.

Wattmeter combination By reason of the substantially constant characteristic impedance of coaxial line terminators or loads of the present character, the power absorption of such devices for a given voltage is substantially constant at all frequencies encountered in practice. Measurement of the voltage across the entering end of the coaxial line device gives a value which varies with the power being absorbed. A useful power measuring instrument or wattmeter is thus obtained. Reference is made to copending application for patent Serial No. 116,318, filed September 17, 1949, now Patent No. 2,702,368, for Method of and Apparatus for Measuring High Frequency Energy which describes more fully and claims the electrical measuring instrument. A wattmeter of such character functions in accordance with the formula:

E2 W R in which W represents the power in watts, E represents the applied potential in volts and R represents the resistance in ohms.

Since, as pointed out heretofore, the value of R represented in the present invention by the characteristic impedence of the coaxial line unit, is substantially constant for all frequencies, the power equation reduces to the following:

K represents a constant over the usual operating frequencies. Measurement of the applied electrical potential or voltage as by a dial type indicating instrument is then conveniently converted as by suitable scale indicia into power or watts which are thus read directly.

Considerable ditficulty has been encountered in obtaining accurate readings of voltages prevailing across coaxial 10 lines and devices of the type herein described. It has been particularly difficult to obtain accurate readings of applied voltages when the device is utilized at different frequencies.

By sampling the applied voltage and actuating a galva nometer preferably of the dArsonval type by the sample voltage or current a satisfactory arrangement has been found. It is desirable, however, to avoid such interference with the high frequency current in the coaxial line as might occur by the extension of a conductor or conductors through the annular space separating the inner and outer conductors of the line.

Capacitance voltage divider Satisfactory sampling of high frequency potentials across or at the entering end of the coaxial line device is obtained by the use of a capacitance voltage divider. The present voltage sampler D, which forms the subject matter of copending application for patent Serial No. 99,474, filed June 16, 1949, now U. S. Patent No. 2,641,827, for Combined Voltage Divider and Crystal Cartridge Assembly for high Frequency Electrical Device and is therein more fully described and claimed, operates effectively over all frequencies at which the wattmeter normallyis used and suitable means is incorporated to provide direct current to the galvanometer circuit proportional to the potential or voltage of the high frequency current flowing into the coaxial line terminating device. It comprises a chambered or hollow body 70 formed of brass or similar conductive metal contoured on one side to conform to the outer surface of the connector 7. The voltage sampler is attached to the connector as by soldering or brazing and is formed with a central chamber 71 which communicates with the annular space between the center connector 27 and the tubular connector 7 through an opening 72 formed in the latter.

Supported within the body 70 is a tree structure comprising a conductive metal stem 73 having a number of angularly disposed radial branches. The stem and branches are insulated from the body 76 and the stem is centered or axially disposed in the chamber 71 which chamber may be formed as by drilling to provide the different diameters. desired. Slidably received in one end of the stem 73 is an adjustable metal probe 74 which projects into and through the opening 72 into the space between the inner and outer connectors of the coaxial line. This probe and the inner or center conductor of the coaxial line B comprise an adjustable capacitor or condenser C-1 to be later referred to in connection with the operation of the wattmeter. The cylindrical probe is circular in section and has a threaded end 75 screwed into internal threads formed in an axial bore within the stem 73. The threaded end of the probe is axially slotted as indicated at 76 and spread slightly prior to assembly so that the threaded parts are frictionally restrained against relative turning and the probe 74 is-retained inwhatever desired position of adjustment to which it is turned. Suchturning adjustment is effected as by means of a hex ended rod passed axially into the stem 73 through a bore 77 and received-in a mating hex socket 78 formed in the body of the probe 74, the body 70 being provided with an aligned opening into the chamber 71.

The ends of the probe and the stem are received and enclosed in a cylindrical flanged cup 80formed of a relatively stiff insulating material such as polytetrafluoroethylene. This cup extends through passage 81 in the connector 7 and into the annularspace between the coaxial line connectors. A threaded counterbore at the inner end of the body passage 81 receives a threaded washer 82 which compresses a washer 83 against the flanged end of t'hecup 80 to hold the cup in place and to provide a fluid-tight seal. The insulating cup 80 thus provides a sealed closure for the passage or opening into the chamber 71 of the capacitance voltage divider D, prer 11 venting liquid dielectric coolant from entering the chamber from the coaxial line structure B.

Another branch of the tree structure is in the form of a cylindrical circular sectioned rod or condenser element 85 which preferably is disposed at a right angle to the stem 73 and which extends laterally through a radial opening 86 in the body 70. The rod 85 is received in a transverse hole 87 drilled through the stem 73 and secured as by soldering to provide a good electrical connection. A conductive metal cap or outer condenser element 88 having a closed end is received over the outer end of the rod 85 and is formed with a reduced diameter end 89 press fitted into the radial passage 86 and soldered in place. A ceramic insulating sleeve 90 surrounds the center condenser element or rod 85 locating the latter in the circular bore of the cap or closed end sleeve 88.

The ceramic sleeve 90 of electrical porcelain or similar material serves as a dielectric between the inner element 85 and the outer element 88 which collectively comprise a coaxial condenser structure C-2, referred to later in connection with the operation of the wattmeter. The ceramic sleeve also locates and supports the tree structure within the conductive metal body 70. While the ceramic sleeve 90 may be fitted over the entire length of the inner element or rod of the condenser it is preferable to provide at one or the inner end a dielectric sleeve 91 of a relatively soft or yieldable material such as polytetrafluoroethylene. The end portion of the yieldable sleeve 90, disposed within the body chamber 71, is confined between the stem 73 and the inner end face of the reduced diameter portion 89 of the condenser outer element or cap 88. A reduced diameter portion on one end of the yieldable sleeve 91 is received within circular bore 92 of the condenser cap and annular shoulder 93 of the insulating sleeve seats against the end of the condenser cap to locate the parts in assembly.

Across the body chamber 71 from the condenser structure C-2 and in diametric relation to such structure is a current rectifier assembly which may be in the form of a dry point contact rectifier, also identified as a converter crystal or a crystal diode. This assembly includes a tubular retainer or sleeve 95 which has a threaded central portion received and held in a threaded radial passage 96 diametrically opposite and axially aligned with the condenser receiving passage 86. The inner end of the crystal retainer 95 is formed with a tapered or frustoconical seal 97 which is engaged by the matching face of a yieldable insulating washer 98 of a suitable dielectric material such as polytetrafiuoroethylene. The gasket or washer 98 is received about a tubular end portion 99 of the rod 85 which projects through the stem 73. The washer also bears against the stem 73, cooperating with the yieldable dielectric sleeve 91 in locating the tree structure in the body cavity 71.

Within the retainer 95 a removable conductive metal sleeve 101 holds a crystal rectifier unit 100. This unit includes a hollow ceramic insulating tube 102 threaded internally at both ends. In one end of the tube a threaded base plug 103 holds an adjustable brass rod on the inner end of which is mounted a semi-conductor crystal 104 of the type having electric current rectifying properties such, for example, as galena or lead sulphide, germanium, or silicon.

The other end of the insulating tube 102 receives a threaded metal plug 107 which carries a spring-like whisker wire 108 that makes point contact with a sensitive spot of the crystal 104. The cavity in the tube 102 is filled through a lateral opening with wax to seal the parts.

The crystal unit 100 is received within the sleeve 101 with a free or loose fit, and is held in place by a conductive metal cap 110 having a thin edge 111 flanged over an annular rib on the sleeve 101. A cushion such as a rubber O-ring 112 is interposed between the end of the cap 110 and the crystal unit 100 and holds flange 109 of the metal plug 103 seated against the end of the sleeve 101 so that 12 the crystal plug makes positive electrical connection with the sleeve and the body of the sampling device D.

The axial passage through the retainer sleeve is counterbored, providing an outer portion 114 of relatively large diameter which receives the outer end of the sleeve 101. An integral circular rib 115 formed on the sleeve 101 seats against the end of the counterbore in the retainer sleeve 95 to locate the crystal holding sleeve in the assembly. A rubber O-ring 116 received about the crystal holding sleeve 101 between the flanged edge 111 of the cap and the locating rib is radially compressed between the body of the crystal holding sleeve and the cylindrical walls of the counterbore 114 to provide a seal which prevents the entry of dust and moisture into the inner end of the crystal assembly. The inner end of the crystal holding sleeve 101 is axially slotted as indicated at 117 to provide a plurality of tines which, having been slightly spread apart prior to assembly, frictionally engage the walls of the retaining sleeve 95 to hold the crystal holding sleeve within the retainer sleeve. The crystal unit may be readily removed from the retainer sleeve 95 by withdrawing the cap 110 and the crystal holding sleeve 101 from the retainer as a unit. Slight misalignment is accommodated by shifting or tilting of the crystal unit 100 within the holding sleeve 101 thus preventing distortion of the crystal unit and avoiding damage to its parts. A link chain 118 connected to the cap 110 and to the body 70 of the capacitance voltage divider serves as a safety fastener to avoid loss and damage by dropping of the crystal unit should the unit become dislodged from the retainer sleeve 95. A satisfactory crystal diode rectifier is one capable of carrying current of about 30 micro amperes with a back potential of about one volt or less, such, for example, as is known in the electronics trade as type 1N21B.

A third branch of the sampling devices tree structure comprises a resistor R, of the insulated metallized type, which is connected in series between the stem 73 and one terminal of a galvanometer G. The other terminal of the galvanometer is connected to the body 70 of the sampling device or voltage divider D. The resistor may take the form of a glass tube 121 (Fig. 11) coated with a metal or carbon film and encased within an insulating body 122. Conductor wires 123 and 12 extend into the glass tube ends and are electrically connected to the resistive carbon coating as by solder or metal cups clamped on the ends of the carbon coated tube. Conductor wire 123 is connected to the stem 73 and conductor wire 124 is connected to a metal terminal plug 125.

The terminal plug 125 is supported as by a body 126 of strong, relatively stiff insulation such as a phenolic resin held by a press fit in externally threaded tubular fitting 127 screwed into a radial opening in the body 70. The inner end of the passage through the tubular fitting 127 is counterbored to receive a condenser or capacitor C-3 of the button type. This capacitor may comprise a centrally apertured circular disc 130 of glass, mica or other insulation separating flanged plates or conductive metal segments on opposite sides. A plate on one side makes electrical connection with the wire 124 through a metal spool 131 which is received in the central aperture of the insulator disc. A plate on the other side of the insulator disc, insulated by such disc from the first mentioned plate, makes electrical connection with the Walls of the counterbore in the metal tube 127 through a metal ring 132 which embraces the periphery of he disc and has a press fit and is soldered in the counterbore. In assembly the capacitor button C3 is disposed against the flanged inner end of the metal terminal 125.

One function of the capacitor button C3 is to bypass the radio or high frequency components of the electrical current in the tree structure and thereby restrict the external galvanometer circuit to the direct current produced by the effect of the crystal rectifier 100. It has been found satisfactory to employ such a condenser having a capacity of about 500 M. M. F.

13 Galvanometer connection Over the outer opening of the tubular fitting 127 is received a side opening connector fitting 133 having a threaded metal swivel collar 134 which engages the threads on the tubular fitting 127. A helical coil impression spring 135 of conductive metal is disposed within a side opening chamber in the upper end of the fitting 123, the spring being insulated from the walls of the metal fitting by a disc 136 and a cup 137 of suitable dielectric or insulating material such as polytetrafluoroethylene. A central aperture in the bottom of the insulating cup 137 admits the round end of the terminal 125 so that the latter makes electrical contact with the bent over end turn of the metal spring 135. A resilient O-ring 138 of material such as rubber is interposed between the side face of the fitting 133 and the end face of the tubular fitting 127 to provide a dust and moisture proof seal. Electrical connection is established between the swivel fitting 133 and the body 76 of the voltage divider D by the metal of the tubular fitting 127 and the collar 134.

The galvanometer G is connected to the voltage divider D preferably by means of a flexible or shielded coaxial cable comprising a central wire or conductor 140 and a flexible sheath 141 of woven wire or the like. The center conductor of the coaxial cable is surrounded by a tube 142 of dielectric insulating material which locates the center conductor in coaxial relation to the woven conductor 141. A protective sheath or covering 143 of suitable wear resistant composition surrounds the woven conductor 141. in attaching the flexible coaxial cable to the swivel fitting 133 the protective outer sheath 143 is stripped away from the end portion of the cable, the woven conductive metal sheath 141 is turned back upon itself, and the center conductor 140 and the tubular insulation 142 are moved axially onto a bore 145 formed in the swivel end fitting 133. The end of the center conductor 140 is bared and extends through a lateral opening in the insulating cup 137, being received and pinched between the turns of the coil 135 which thus makes electrical connection therewith. The outer end of bore or passage 145 in the swivel fitting is formed with a counterbore having inner tapered and outer threaded portions. A threaded ferrule 146 surrounds the flexible cable and compresses jam washers in the tapered portion of the counterbore to clamp the end of the flexible cable and to eifect positive electrical connection between the woven conductive sheath 141 and the fitting 133. 1 eference is made to copending application for U. S. patent, Serial No. 173,776, filed July 14, 1950, now U. 3. Patent No. 2,635,297, for Electrical Connector, which describes and claims the cable connecting means.

In connecting the galvanometer 9 in series between the body of the voltage divider D and the resistor R one terminal of the galvanometer is connected to the center conductor 14b and the other terminal is connected to the conductive sheath or outer conductor 141 of the coaxial cable, these parts being diagrammatically represented in Fig. 8. This arrangement in which the galvanometer is connected to the voltage divider by means of a coaxial cable protects the sensitive galvanometer from stray high frequency radiations which are frequently encountered in the vicinity of television and other high frequency electrical apparatus.

After assembly of the voltage divider D the chamber 71, which is formed with an opening through the end of the body 70, is closed as by a threaded metal plug 148.

Wattmeter operation In the operation of the device of the present invention for the purpose of measuring electrical energy or power the coaxial line B is connected to the output of a suitable high frequency power generating device such as a television transmitter, the connection being made to the tubular fitting 17 in accordance with conventional practice. Power thus fed into the device is converted into heat by 14 or in the resistive coating on the center conductor 24. The heat is absorbed by the liquid dielectric coolant which circulates or is circulated as by convection through the chambers 45 and 46 and through the annular space 31 between the conductors of the coaxial line structure B.

The casing or tank 1 is relatively tall or deep, being preferably at least about twice the height of the resistive coaxial line to be cooled. By this arrangement the baffle 47, which is arranged as by apertures or otherwise to provide at its upper end for passage of the liquid from one casing chamber to the other, can be made sufiiciently tall to obtain a substantial chimney effect for improving the convective circulation of the liquid within the casing. In the present arrangement top edge 65 of the baffle terminates below the surface level 56 of the liquid so that heated liquid, after rising through the chimney baffie, flows laterally over the upper edge or edges of the 'baifie and thence downwardly over the cooling coil 50 through the annular outer or surrounding chamber 46. By reason of the line contact engagement by bottom edge 66 of the chimney baffle against the outer conductor 5 of the coaxial line A, all of the cooled liquid flowing down the annular outer chamber 46 flows into the space 31 between the coaxial line conductors. The liquid heated by contact or by convection or radiation then flows upwardly and outwardly through the upper group or groups of the slots 30 which communicate with the inner bafile chamber 45. The annular space 36 within the cylindrical portion 32 at the upper or small diameter end of the resistive line permits the liquid to flow effectively over the entire coated or resistive surface of the inner conductor 24 to avoid the formation of localized hot spots which might otherwise be objectionable, injurious, or destructive to the ceramic tube.

The upward movement of the liquid through the inner chimney chamber 45 under the buoyant influence of the vapor particles continuously and of the lowered density of the relatively hot body of coolant within the dielectric space 31 and the chimney chamber 45 draws fresh coolant in through the bottom group or groups of the elongated openings 30 from the outer chamber 46. The incoming coolant, in entering the annular dielectriccoolant space surrounding the center conductor 24 adjacent the large diameter bottom end of the outer conductor or horn 5, flows upwardly through a coolant space which progressively reduces in cross sectional area. The upward flowing liquid sweeps or scrubs rapidly and at a high rate longitudinally over the hot surface of the resistive coating on the center conductor 24, cooling the latter effectively and entraining or carrying away previously formed vapor bubbles of the dielectric coolant. The vapor bubbles moving upwardly in the rising liquid coolant have the additional effect of creating a turbulence in the mixed phase dielectric which reduces laminar flow and thereby results in a vigorous churning or mixing of the rising mass so that the volatilized liquid is cooled as it moves upwardly and is substantially completely condensed or returned to the liquid phase at or prior to reaching the upper end of the chimney baffle 47. Vapor bubbles or particles which do not break through the surface of the liquid and which are not completely condensed by the surrounding liquid during the upward travel through the chimney bafile, being of relatively small size and having but negligible buoyant effect, are carried over the top of the baffle and descend with the liquid dielectric-coolant through and between the turns of the cooling coils 50 where condensation and absorption of the vapor is completed. The liquid is omitted from the drawing illustrations to avoid confusion but fills the casing up to the level indicated by the line 56. Thus the upper surface of the liquid is located between the upper edge of the chimney baffle and the bottom of the outlet vent pipe 55, rising and falling within these limits during thermal expansion and contraction of the liquid. In the event of an extreme overload resulting in vapor particles breaking through the liquid surface 56, the upward movement of the vapor through the spiral passage formed by the fins of the cooling tube in the inlet conduit 52 results in condensation of the liquid prior to reaching the vent 55. The condensate fiows by gravity down through the passage and is returned to the chambers 45 and 46.

During operation of the present device in absorbing high frequency electrical power, the voltage drop or potential difference across the input end of the coaxial load B between the center tapered connector 27 and the surrounding or outer tapered connector 7 is divided between the condensers C-1 and -2 inversely proportional to the capacitances of the respective condensers. Capacitance C1, comprising the inner connector 27 and the probe 14, is relatively small with respect to the coaxial condenser C-Z. Accordingly the voltage drop across C2 is a small but uniformly proportional fraction or sample of the total voltage impressed upon the device, the relationship remaining substantially constant over a wide frequency range. Similarly the voltage drop across the crystal rectifier 100, being the same as the voltage across the condenser C-2, remains a constant small sample or fraction of the main voltage applied across the coaxial line B.

During one half of each cycle of the alternating or high frequency current, electrical current flows through the crystal rectifier 100 and prevents the condenser from being discharged, thereby producing a peak charge on the condenser. During the other half of each cycle reverse flow of electrical current through the crystal is prevented by the inherent nature of the rectifier and the condenser C-2 tends to become or remain charged by displacement current flow. Thus the condenser C-2 remains charged with a direct current voltage substantially equal to the peake voltage of the high frequency alternating sample current.

The resistor R is used in series with the galvanometer G to prevent discharging of the condenser 0-2. A relatively high resistance, of the order of about 30,000 ohms, is employed in the resistor R so that the time constant of the resistor and the condenser C-Z combination is sufiiciently large to maintain the charge on the condenser C-2 relatively close to the peak voltage of the sample high frequency current. The high resistance provides a substantially flat curve response in the galvanometer circuit at all frequencies within the designed range. In addition to its functions in the galvanometer circuit maintaining the condenser C-Z charged to peak voltage and providing a flat response at all frequencies, the resistor R isolates the high frequency current from the galvanometer G. The high resistance in series in the galvanometer circuit effects a by-pass of the high frequency current through the button condenser C-3 shunted across the galvanometer. In this manner undesirable high frequency voltages are substantially eliminated from the galvanometer circuit by the resistance-capacitance filter combination.

Since the action of the crystal combined with other elements of the galvanometer circuit as described herein tends to maintain condenser C-Z charged substantially to the peak voltage of the sample current, a direct current of small magnitude is provided for continuous flow through the galvanometer circuit. The galvanometer circuit sample current is substantially in constant proportion to the peak voltage across the coaxial resistor device B. Hence the galvanometer, indicating directly the sample current in the galvanometer circuit likewise indicates directly at reading substantially proportional to the peak voltage of the main coaxial line circuit.

The reading on the galvanometer dial thus varies directly with and is in substantially constant proportion to the peak voltage applied to the coaxial resistor device B. The galvanometer, by suitable calibration of its dial, is thus made to indicate directly the high frequency power being absorbed in the resistor. Such calibration is in accordance with the principles and formula set forth above in connection with the description of the wattmeter combination and may be empirically determined as by comparing the present device with known power measuring instruments. The calibration of the galvanometer scale to indicate power consumed or absorbed is thus predicated on squared values of the voltages to which the galvanometer is subjected. Accordingly, calculated calibration is subject to suitable modification by reason of the fact that power determination in an alternating current system is based on average voltage, a constant fraction of peak voltage.

One of the characteristics of crystal rectifiers of the type used in the present device is sensitivity increase upon increase in the frequency of the alternating electric current applied to the crystal. This characteristic is exhibited over the frequency range below the natural frequency of the crystal. Thus, in the range below such natural frequency an increase in the direct current output of the crystal occurs as the frequency of the high frequency current in the coaxial device increases. This increase in sensitivity or current output in the crystal occurs even though the potential or voltage of the high frequency alternating current remains constant. It is believed that the construction of the crystal unit, which combines a Whisker wire with a semiconductor mineral produces a resonant effect. Compensation for this frequency sensitive response of the crystal is obtained in the present Wattrneter or voltage measuring instrument by the construction and arrangement of the condenser C2 which is in the form of a coaxial stub capacitor hiving characteristics over the designed frequency range of the device that compensate for the changes in crystal sensitivity over the same frequency range.

With increasing frequency the coaxial stub capacitor characteristically decreases in impedance as measured across its input end. Thus the coaxial capacitor response tends to drop off as its electrical length increases or approaches one quarter wave. By electrically connecting the crystal rectifier and the coaxial stub capacitor in parallel in the manner shown, the responses of the two components being balanced against one another over the designed frequency range as by adjustment of the electrical length of C2, the capacitor has the effect of compensating for the changes in rectifier sensitivity of the crystal to obtain a response or output from the sampling device D which is substantially constant over a wide frequency range.

In accordance with the patent statutes the principles of the present invention may be utilized in Various ways, numerous modifications and alterations being contemplated, substitution of parts and changes in construction being resorted to as desired, it being understood that the particular apparatus and combination shown in the drawings and described above are given merely for purposes of explanation and illustration without intending to limit the scope of the claims to the specific details disclosed.

What we claim and desire to secure by Letters Patent of the United States is:

1. In a high frequency electrical device of the character described, inner and outer spaced conductors arranged in a coaxial line, baffie means surrounding one end of the line in spaced relation, a casing surrounding the conductors and the baffle means for containing a liquid dielectric and coolant to immerse the conductors and the baffle means, the baffie means dividing the casing into chambers one within the other, and the outer conductor being formed with apertures for the flow of liquid dielectric and coolant between each of the chambers and the space between the conductors.

2. In a high frequency electrical device of the character described, a resistive coaxial line comprising an inner conductor and an apertured outer conductor joined at one end, said conductors being separated by an annular dielectric space progressively reducing in cross sectional area toward said one end, and easing means providing separate chambers for containing liquid dielectric, one casing chamber being in communication with the space between the line conductors only through apertures in the outer conductor adjacent said one end of the coaxial line and another chamber being in communication with said space only at a point remote from said one end of the line.

3. In a high frequency electrical device of the character described, a casing for containing a liquid dielectric and coolant, a resistive coaxial line and means supporting the same in the casing with the line axis substantially vertical, the line comprising inner and outer spaced conductors, one of which is apertured for the flow of liquid into and out of the space between the conductors, and an elongated tubular baffle supported within the casing with the long axis of the tube substantially vertical to divide the casing into chambers, the bafile having connection with the apertured conductor so that one chamber communicates directly with the space between the conductors only through one group of apertures and another chamber communicates directly with said space only through another group of apertures, the chambers being connected remote from the line for serial flow of liquid through the chambers and said space.

4. A high frequency electrical device having inner and outer spaced conductors arranged in a coaxial line, one of said conductors being resistive to convert electrical energy into heat casing means about the line, a volatilizable liquid dielectric coolant in the casing means and immersing the line, said liquid being a halogenated hydrocarbon having a boiling point between about 70 C. and about 160 C., and means including a bafiie extending downwardly from above the line into proximity to one of the conductors of the line to provide a chamber generally above the line for confining the flow of volatilized dielectric-coolant to a predetermined path in the casing means above the line whereby to control the convective flow of liquid in the casing means.

5. In a high frequency electrical device of the character described having inner and outer conductors arranged in a coaxial line and electrically connected together at one end of the line, the inner conductor being relatively resistive in character and of substantially uniform circular section along its length and the outer conductor being tapered and of substantially circular section along its length, an improved end connection for the conductors comprising a substantially cylindrical structure at the small diameter end of the outer conductor spaced from and surrounding one end of the inner resistive conductor, a conductive element disposed Within said one end of the inner resistive conductor, said element being of substantially the same length as the cylindrical structure, and means electrically connecting the conductive element and the cylindrical structure.

6. In a high frequency electrical device of the character described, inner and outer spaced coaxially arranged conductors, a casing about the conductors for containing a liquid dielectric and coolant to immerse the conductors, one conductor being resistive, one conductor being tapered along its length, and one conductor being apertured for the flow of liquid dielectric and coolant therethrough into and out of the space between the conductors, and baffle means dividing the casing into .chamhers, said bafile means having connection with an intermediate zone of the apertured conductor, one of thechambers being in communication with said space through apertures in one portion of the apertured conductor and another chamber being in communication with said space through apertures in another portion of the apertured conductor.

7. In a high frequency electrical device of the character described having an inner resistive conductor and an outer tapered conductor coaxial to the inner conductor, a casing about the conductors for containing a liquid dielectric and coolant to immerse the conductors, and bafile means having connect on With the outer conductor at an intermediate point along the length of the latter, the battle means dividing the easing into chambers each communicating with the space between the conductors through apertures in the tapered outer conductor and the chambers being in communication with one another only in a zone remote from the conductors to guide liquid dielectric and coolant for circulation serially through the chambers and the space between the conductors 8. In a high frequency electrical device of the character described, inner and outer spaced coaxially arranged conductors, a casing about the conductors for containing a liquid dielectric and coolant to immerse the conductors, one of the conductors being resistive, one of the conductors being apertured, and one of the conductors being tapered along its length, and baffle means dividing the casing into. chambers, each chamber being in communication through the apertured conductor with the space between the conductors, the baffle means being connected to the apertured conductor and the chambers being in communication with one another remote from the apertured conductor whereby liquid flow between said space and one of the chambers induces liquid flow between another of the chambers and said space.

9. In a high frequency electrical device of the character described, inner and outer spaced coaxially arranged conductors, the inner conductor being resistive and the outer conductor being tapered and apertured, a casing disposed about the conductors for containing a liquid dielectric and coolant to immerse the conductors for'the flow of liquid into and out of the space between the conductors, and bafiie means dividing the casing into chambers each communicating with said space through the apertures in the outer conductor, and the chambers being separated from one another at the outer conductor to prevent cross flow of liquid between chambers in the region of the conductors other than through the space between the conductors.

10. In a high frequency electrical device of the character described, a casing having a hollow interior, spaced inner and outer conductors arranged in a coaxial line, one of the conductors including an elongated relatively resistive portion for absorbing electrical energy fed into the line, a liquid coolant in the casing, means supporting the line in and in predetermined fixed relation to the casing with the longitudinal axis of the resistive portion of the one conductor in an upright position and with such resistive portion substantially immersed in the coolant, and 'baffle means substantially surrounding both inner and outer conductors, said baflie means dividing the casing interior into chambers and extending longitudinally and vertically over at least part of the resistive conductor portion, the baffle means being immersed in the coolant and having a top portion formed and positioned below the surface of the liquid coolant for the flow of such liquid coolant horizontally from one to another of the chambers at the top of the casing, and one of the conductors being formed with apertures placing the space between the conductors in communication with a plurality of the chambers for serial flow of the coolant through the chambers and the space between the conductors.

11. In a high frequency electrical device of the character described, a casing having a hollow interior, spaced inner and outer conductors arranged in a coaxial line, one of the conductors including an elongated relatively resistive portion for absorbing electrical energy fed into the line, a liquid coolant in the casing, means supporting the line in and in predetermined fixed relation'to the Casing with the longitudinal axis of the resistive portion of the one conductor in an upright position and with such resistive portion substantially immersed in the coolant, baffle means substantially surrounding both inner l 9 and outer conductors, said baflle means dividing the easing interior into chambers and extending longitudinally and vertically over at least part of the resistive conductor portion, the baffle means being immersed in the coolant and having a top portion formed and positioned below the surface of the liquid coolant for the flow of such liquid coolant horizontally from one to another of the chambers at the top of the casing, and one of the conductors being formed with apertures placing the space between the conductors in communication with a plurality of the chambers for serial flow of the coolant through the chambers and the space between the conductors, and a cooling fluid tube immersed in the coolant substantially wholly outside the bafiie means, the tube being adapted for the flow of fluid therethrough to absorb and carry oif heat from that part of the liquid coolant located in a zone outside the baflie means.

12. In a high frequency electrical device of the character described, a casing having a hollow interior, spaced inner and outer conductors arranged in a coaxial line,

one of the conductors including an elongated relatively resistive portion for absorbing electrical energy fed into the line, a liquid coolant in the casing, means supporting the line in one end of the casing with the resistive portion of the one conductor in an upright position and immersed in the coolant, and baffle means substantially surrounding both inner and outer conductors, said battle means dividing the casing interior into chambers and extending axially and vertically beyond the resistive conductor portion toward the other end of the casing, the baflle means being immersed in the coolant and having a top portion formed and positioned below the surface of the liquid coolant for the flow of such liquid coolant horizontally from one to another of the chambers at the top of the casing, and one of the conductors being formed with apertures placing the space between the conductors in communication with a plurality of the chambers for serial flow of the coolant through the chambers and the space between the conductors, and the extent of the baffle means beyond the resistive conductor portion providing a chimney effect conducive to said serial flow.

13. In an electrical device of the character described, inner and outer spaced coaxial conductors, the outer conductor including a substantially cylindrical end portion of relatively thin metal, a casing about the conductors for containing a liquid dielectric coolant, said casing including a wall formed with a substantially circular aperture and substantially circular flange means surrounding the aperture, the wall and the flange means providing a substantially cylindrical inwardly directed guide surface, an outer connector for joining the outer conductor to a line, said connector including a substantially cylindrical end portion in telescoped relation to the end portion of the outer conductor, one of the cylindrical end portions extending through and being closely embraced by the cylindrical guide surface of the circular flange means and the casing wall, means securing one of the cylindrical end portions to the circular flange means for mounting the outer conductor and connector on the casing wall in predetermined fixed relation, and liquid dielectric coolant in the casing, the conductors being immersed in the liquid.

14. In an electrical device of the character described, inner and outer spaced coaxial conductors, the outer conductor including a substantially cylindrical end portion of relatively thin metal, a casing about the conductors for containing a liquid dielectric coolant, said casing including a wall formed with a substantially circular aperture and substantially circular flange means surrounding the aperture, an outer connector for joining the outer conductor to a line, said connector including a substantially cylidrical end portion in telescoped relation to the end portion of the outer conductor, one of the cylindrical end portions extending through and being closely em-- braced by the flange means, one of the cylindrical end 2'3 portions being formed with an angularly disposed end flange, a clamping ring embracing both the circular flange means and the end flange for holding the parts together in predetermined relation, and liquid dielectric coolant in the casing, the conductors being immersed in the liquid 15. In a high frequency electrical device of the character described having inner and outer conductors arranged in a coaxial line, at least one of the conductors being resistive and at least one of the conductors being tapered and having large and small ends to provide at points spaced along the length of the line calculated characteristic irnpedances substantially equal to the resistances of the line measured between the conductors at the respective points, an improved connection between the small end of the tapered conductor and the other conductor, said connection comprising a relatively short conductor disposed in telescoped relation to and within both said inner and outer conductors, said short conductor being connected to the tapered conductor at the small end of the latter, and the inner and outer conductors being formed to make electrical contact with one another substantially at the small end of the tapered conductor and in a plane displaced toward the large end of the tapered conductor from the plane of the connection between the tapered and short conductors.

16. In a high frequency electrical device of the character described having inner and outer conductors arranged in a coaxial line, at least one of the conductors being resistive and at least one or" the conductors being tapered and having large and small ends to provide at points spaced along the length of the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, an improved connection between the small end of the tapered conductor and the other conductor, said connection comprising a relatively short tubular conductor disposed in telescoped coaxial relation to said inner and outer conductors, means electrically connecting one end of the short tubular conductor to the small end of the tapered conductor, and the inner and outer conductors being formed to make electrical contact with one another substantially at the small end of the tapered conductor and in a plane displaced toward the large end of the tapered conductor from the plane of the connection between the tapered and short conductors.

17. In a high frequency electrical device of the character described having inner and outer conductors arranged in a coaxial line, at least one of the conductors being resistive and at least one of the conductors being tapered and having large and small ends to provide at points spaced along the length of the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, an improved connection between the small end of the tapered conductor and the other conductor, said connection comprising a relatively short conductor connected at one end to the small end of the tapered conductor and extending within the resistive conductor in spaced relation to the latter, said short conductor substantially conforming in cross sectional shape to the resistive conductor and with such resistive conductor comprising a capacitive coupling between the inner and outer conductors, andthe inner and outer conductors being formed to make electrical contact with one another substantially at the small end of the tapered conductor and in a plane displaced toward the large end of the tapered conductor from the plane of the connection between the tapered and short conductors.

18. A high frequency electrical resistive device comprising inner and outer conductors arranged as a coaxial line, at least one of the conductors being resistive and at least one of the conductors being tapered, casing means enclosing the line, a liquid dielectric coolant in the casing, the conductors being immersed in the liquid, said conductors being separated by an annular dielectric space which tapers in cross sectional area substantially from one end of the line to the other, one of the conductors being formed with slots at that end of the line having a dielectric space of relatively small cross sectional area, said slots being arranged for the flow of said liquid through the small area dielectric space in direct heat exchanging contact with the resistive conductor, and a relatively short conductor connected at one end to the slotted conductor, said short conductor being disposed in telescoped relation to the resistive conductor and with such resistive conductor comprising a capacitive coupling between the inner and outer conductors.

19. A high frequency electrical resistance drive comprising a tapered outer conductor and a resistive material inner conductor arranged in spaced relation as a coaxial line in which the space between the conductors tapers in cross sectional area along the length of the line to provide at points along the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, the outer conductor being formed with apertures for the flow of fluid dielectric coolant into and out of said space in direct heat exchanging contact with the resistive material conductor, some of said apertures being adjacent one end of the line which has a dielectric space of relatively small cross sectional area, the dielectric space along a port-ion of the line adjacent said one end being of greater cross sectional area than required for said calculated characteristics to obtain an increased rate of flow of fluid dielectric coolant through the dielectric space in said line end portion, and a relatively short conductor connected to the outer conductor and disposed in spaced coaxial relation to the resistive material conductor, said short conductor and the resistive material conductor comprising a capacitive coupling substantially compensating for the departure from calculated characteristics incident to the presence in said line end portion of the said greater dielectric space.

20. A high frequency electrical resistive device comprising a tapered horn conductor and a substantially cylindrical resistive material conductor arranged in spaced relation as a coaxial line in which the space between the conductors tapers in cross sectional area along the length of the line to provide at points along the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, the horn conductor being formed with apertures for the flow of fluid dielectric coolant into and out of said space in direct heat exchanging contact With the resistive material conductor, some of said apertures being adjacent one end of the line which has a dielectric space of relatively small cross sectional area, the dielectric space along a portion of the line adjacent said one end being of greater cross sectional area than required for said calculated characteristics to obtain an increased rate of flow of fluid dielectric coolant through the dielectric space in said line end portion, a relatively short substantially cylindricalconductor disposed in telescoped relation to the resistive material conductor at said line end portion, and means connecting the short conductor tothe horn conductor at said one end of the line, said short conductor and the resistive material conductor comprising a capacitive coupling substantially compensating for the departure from calculated characteristics incident to the presence in said line end portion of the said greater dielectric space.

21. A high frequency electrical resistive device comprising a tapered horn conductor and a substantially cylindrical resistive material conductor arranged in spaced relation as a coaxial line in which the space between the ,conductorstapers in cross sectional area along the length of the line to provide at points along the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, the horn conductor being formed with apertures for the flow of fluid dielectric coolant into and out of said space in direct heat exchanging contact with the resistive material conductor, some of said apertures being adjacent one end of the line which has a dielectric space of relatively small cross sectional area, the dielectric space along a portion of the line adjacent said one end being of greater cross sectional area than required for said calculated characteristics to obtain an increased rate of flow of fluid dielectric coolant through the dielectric space in said line end portion, a relatively short substantially cylindrical conductor disposed in telescoped relation to the resistive material conductor at said line end portion, and means rigidly connecting one end of the short cylindrical conductor to one end of the horn conductor at said one end of the line, the connecting means being formed with slots permitting relative expansion and contraction of the horn and the short conductor, said short conductor and the resistive material conductor comprising a capacitive coupling substantially compensating for the departure from calculated characteristics incident to the presence in said line end portion of the said greater dielectric space.

22. A high frequency electrical resistive device comprising a tapered horn conductor and a substantially cylindrical resistive material conductor arranged in spaced relation as a coaxial line in which the space between the conductors tapers in cross sectional area along the length of the line to provide at points along the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, the horn conductor being formed with apertures for the flow of fluid dielectric coolant into and out of said space in direct heat exchanging contact with the resistive material conductor, some of said apertures being adjacent one end of the line which has a dielectric space of relatively small cross sectional area, the dielectric space along a portion of the line adjacent said one end being of greater cross sectional area than required for said calculated characteristics to obtain an increased rate of flow of fluid dielectric coolant through the dielectric space in said line end portion, and a short conductor disposed within said line end portion in coaxial relation to the line, the short conductor and the horn conductor each including integral extensions rigidly secured together beyond said one end of the line, said conductor extensions being formed for relative expansion and contraction, the resistive material conductor being receivable about the short conductor in assembly and being disposed between the short conductor and the horn conductor, means'electrically connecting the resistive material and horn conductors together at said one end of the line, said short conductor and the resistive material conductor comprising a capacitive coupling substantially compensating for the departure from calculated characteristics incident to the presence in said line end portion of the said greater dielectric space.

23. In a high frequency electrical device of the character described, inner and outer spaced conductors arranged in a coaxial line, a casing about the line for containing a liquid dielectric and coolant to immerse and absorb heat from the line, one of the conductors being tapered to a relatively small diameter end and the line being supported in the casing with the axis of the line substantially vertical and with said small diameter end uppermost and bafile means in the casing and co-acting with the line to direct convective flow of liquid, said bafile means including a chimney portion disposed about the small diameter end of the one conductor and extended an appreciable distance above the line to confine heated liquid rising convectively from the line, said chimney portion being shaped to receive at its lower end substantially all of the liquid flowing convectively over the line whereby to confine all the heated liquid in a buoyant mass.

24. In a high frequency electrical device of the character described, a resistive coaxial line comprising inner and with one another for the flow of liquid dielectric therebetween, and a liquid dielectric continuous in the chambers and the dielectric space for serial flow therethrough by gravity action.

25. In a high frequency electrical device of the character described, a resistive coaxial line having spaced inner and outer conductors concentrically arranged, a casing for containing a liquid dielectric and coolant, means supporting the coaxial line in the casing with the axis of the line substantially vertical, means dividing the easing into chambers, means placing each of the chambers in communication with the space between the line conductors for the serial flow of liquid through the chambers and said space, and electric switch means for a warning circuit to indicate the presence of excessive temperature in the casing, said switch means being supported by the casing and including a thermal responsive element disposed above and in substantially vertical alignment with the chamber which receives liquid dielectric coolant from said space.

26. A high frequency electrical resistor comprising a casing for containing liquid dielectric coolant, said casing having a line supporting bottom, inner and outer conductors arranged in spaced relation as a coaxial line, at least one of said conductors being resistive, means supporting the line in and substantially wholly by the bottom of the casing with the axis of the line substantially vertical, coaxial connector means carried substantially wholly by the bottom of the casing and connected to the inner and outer conductors for connecting the line in a high frequency circuit, a liquid dielectric coolant in the casing, one of the conductors being formed with apertures for admitting said liquid to flow into and out of the space between the conductors in cooling the resistive conductor, and bafile means guiding the fiow of liquid in the casing, said baffle means acting to guide liquid moving in the casing to flow substantially axially of the line in the space between the conductors over substantially the entire length of the resistive conductor.

27. In a high frequency electrical device of the type comprising an inner resistive conductor and a tubular metal outer conductor arranged in a coaxial line and in which the inner conductor comprises a substantially cylindrical ceramic tube carrying a deposited resistive film, improved means for connecting the inner and outer conductors at one end of the line, said connecting means comprising an element received snugly within the ceramic tube at said end of the line, means securing the element to the metal outer conductor, said securing means being adapted to retain the element centered in the outer conductor to thereby locate the ceramic tube in coaxial relation to the outer conductor, and means effecting electrical connection between the tubular metal conductor a and the resistive film at said end of the line.

28. In a high frequency electrical device of the type comprising an inner resistive conductor and a tubular 'improved means for connecting the inner and outer conductors at one end of the line, said connecting means comprising a tubular metal element secured to the tubular conductor along a line of connection disposed in a plane "transverse to the longitudinal axis of the line and disr 24- V posed within the ceramic tube at said end of the line, the element and the outer conductor being formed with axial slot means continuous across said line of connection and being resilient to permit yielding expansion and contraction, and the ceramic tube being yieldingly gripped between the element and the tubular conductor.

29. In a high frequency electrical device of the character described, inner and outer coaxially arranged conductors separated by an annular dielectric space, a casing about the conductors for containing a liquid dielectric and coolant to immerse the conductors, one of the conductors being resistive, one of the conductors being tapered along its length, and one of the conductors being apertured for the flow of liquid dielectric and coolant radially therethrough into and out of the annular space between the conductors, and baflie means dividing the casing into chambers said baffie means being located to place one of the chambers in communication with the annular dielectric space through one portion of the apertured conductor and another of the chambers in communication with the said annular dielectric space through another portion of the apertured conductor.

30. A high frequency electrical device having inner and outer spaced conductors arranged in a coaxial line, one of said conductors being resistive to convert electrical energy into heat, means supporting the line with its axis substantially vertical, casing means and a volatilizable liquid dielectric therein immersing the supported line, said volatilizable liquid being volatilizable in the operation of the device at a temperature below the normal operating temperature of the resistive conductor, and bafile means also immersed in the liquid, said baffie'means substantially surrounding a portion of the line and extending above the line to confine volatilized dielectric to a predetermined path in moving upwardly from the line whereby the buoyant eifect of the volatilized liquid is concentrated in said path to control the convective flow of liquid in the casing means.

31. In a high frequency electrical device of the character described, a resistive coaxial line having spaced inner and outer conductors, cooling means for the line comprising a casing for containing liquid dielectric and coolant and for receiving the line so that the latter is immersed in the liquid, the outer conductor of the line being formed with apertures for the flow of liquid dielectric coolant into and out of the space between the conductors and baffle means within the casing dividing the interior thereof into chambers, said baffle means being located to place some of the outer conductor apertures in communication with one of the chambers and others of the said outer conductor apertures in communication with another of the chambers and the chambers in communication with one another for serial flow of said liquid through the chambers and the said space.

32, In a high frequency electrical device of the character described having inner and outer conductors arranged in a coaxial line, at least one of the conductors being resistive and at least one of the conductors being tapered, the conductors being separated from one another by an annular clearance space extending along the length of the line, said space being of relatively large radial dimension at one end of the line and the conductors being formed progressively to approach one another toward and connected together at the other end of the line to provide at points spaced along the length of the line calculated characteristic impedances substantially equal to the resistance along the resistive conductor between the respective points and said other end of the line, the radial dimension of the separating space over a relatively short portion of the line at said other end of the line being greater than required to obtain the calculated impedances along such short line portion in the provision of clearance space between the conductors along such short portion of the line adequate for the flow therethrough of a fluid coolant at a rate suflicient to maintain the conductors within a practical operating temperature range, and a relatively short conductive element in telescoped relation to the short portion of the line, said conductive element being electrically connected to one and in capacitive relation to the other of the conductors at said other end of the line to effect a capacitor coupling between the conductors along the short portion of the line in compensation of the departure along the length of the short portion of the line from the cal culated impedances which results from the greater radial dimension of the clearance space.

33. The method of converting electrical energy into heat in an elongated electrical device of the type comprising conductors separated by a dielectric space, one of said conductors being in the form of a thin resistance film coated on and supported by an insulator, which method comprises simultaneously feeding electrical energy into one end of the device whereby the resistance film conductor is heated, and flowing a liquid halogenated hydrocarbon dielectric coolant of relatively low viscosity, low dielectric constant and which volatilizes at a temperature below the normal operating temperature of the resistance film through the dielectric space in a direction parallel to the surface of the resistance film substantially symmetrical about and from one end to the other of the latter, in intimate heat exchanging contacting relation to the film, and in a continuous stream.

34. The method of cooling an electrical resistive device of the type comprising a pair of elongated conductors each of circular section arranged concentrically and separated from one another by an elongated annular dielectric space to form an elongated coaxial line several times greater in length than in maximum diameter, at least one of the conductors comprising a thin relatively resistive film elongated axially of the line, which film becomes heated by the conduction of electrical energy in the normal operation of the device, which method comprises flowing a halogenated hydrocarbon liquid dielectric coolant having a low dielectric constant which volatiiizes at a temperature below the normal operating temperature of the resistive film conductor in direct contacting heat exchanging relation to the latter over a closed path which includes a portion extending through the annular dielectric space and a cooling zone portion external to the dielectric space whereby the heated resistive film is cooled by the transfer of heat to the liquid in volatilizing the latter and gas particles of the volatilized liquid so formed at the surface of the film resistor form bubbles which by their buoyant effect induce convection currents in the liquid at and adjacent the filni surface to aid in the flowing of the liquid into intir'riate contact with such resistive film, and cooling the liquid in said external cool= ing zone portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,112,733 Burnham Mar. 29, 1938 2,147,481 Beetlestone et al. Feb. 14, 1939 2,154,685 Lamb Apr. 18, 1939 2,273,547 Von Radinger Feb. 17, 1942 2,379,047 Thomas June 26, 1945 2,409,599 Tiley Oct. 15, 1946 2,416,694 Howard Mar. 4, 1947 2,438,915 Hansen Apr. 6, 1948 2,443,637 Ovrebo June 22, 1948 2,453,283 Tiley et al Nov. 9, 1948 2,453,645 Tiley Nov. 9, 1948 2,463,428 Rieke Mar. 1, 1949 2,495,733 Kandoian Jan. 31, 1950 2,529,436 Weber Nov. 7, 1950 OTHER REFERENCES Article: Coaxial-type water load and related powermeasuring apparatus, by Shaw and Kischer, published in Proceedings of Institute of Radio Engineers, vol. 35, pp. 84-87, January, 1947. 

1. IN A HIGH FREQUENCY ELECTRICAL DEVICE OF THE CHARACTER DESCRIBED, INNER AND OUTER SPACED CONDUCTORS ARRANGED IN A COAXIAL LINE, BAFFLE MEANS SURROUNDING ONE END OF THE LINE IN SPACE RELATION, A CASING SURROUNDING THE CONDUCTORS AND THE BAFFLE MEANS FOR CONTAINING A LIQUID DIELECTRIC AND COOLANT TO IMMERSE THE CONDUCTORS AND THE BAFFLE MEANS, THE BAFFLE MEANS DIVIDING THE CASING INTO CHAMBERS ONE WITHIN THE OTHER, AND THE OUTER CONDUCTOR BEING FORMED WITH APERTURES FOR THE FLOW OF LIQUID DIELECTRIC AND COOLANT BETWEEN EACH OF THE CHAMBERS AND THE SPACE BETWEEN THE CONDUCTORS. 